Rosa Xia, a 39-year-old mother in Shanghai, is allowed to have a second child. She does not think she can afford it.

She said a fifth of the 6,000 yuan (US$989) a month she earns as a Shanghai nanny goes to her 12-year-old daughter, Amy: saxophone and ballet lessons, on top of food and school. Then there is the saving for her only offspring’s college education.

She said that her daughter saw people playing saxophone on TV, got interested and asked for lessons.

“It was expensive, so of course I would rather she hadn’t have asked, but I gave it to her anyway,” said the migrant worker, who scrimps on clothing and her own meals to give her daughter the chance of a better future.

Parents like Xia help explain why China’s move to ease family-planning rules is unlikely to reverse falling Chinese birth rates that have saddled the country with a shrinking labor pool and aging population.

While lifting the restrictions — imposed through fines, forced abortions and sterilization — may prove popular in China and with rights advocates abroad, attempts to unpick the state meddling with family sizes face roadblocks from Confucian tradition, urbanization and the rising costs and especially expectations wrought by China’s economic resurgence.

“The fact is, a huge change in mentality about family, children and future is evident,” said Nicholas Eberstadt, a demographer at the American Enterprise Institute, a Washington-based policy group. Cost is at the forefront of the minds of many parents.

Congress in late November last year approved rules that allow couples to apply for permission to have a second child, where either parent is an only offspring. That loosened the policy that allowed a second baby, if both parents are only kids.

China introduced the one-child policy in 1979 after the population jumped more than 70 percent in the three decades following the Chinese Communist Party’s civil war victory, even as the economy stagnated.

In fact, China’s annual population growth was already in decline. It had dipped below 1 percent five years earlier and has not breached the mark since.

“They share common cultural values that place enormous emphasis on the success of their children,” said Wang Feng (王豐), a sociology professor at University of California, Irvine. “Chinese parents want their children to be successful, and they do this by having fewer and investing in them.”

Such aspirations have thrown up a group of so-called “tiger moms,” made famous by author Amy Chua in a book describing strict, disciplinarian Chinese mothers.

The corollary is inflation, both in the money and the time it takes to rear a child as parents wage an arms race to secure the best of the limited opportunities available — raising the barrier to entry for a second child.

For example, to get into a good school, many parents pay a large sponsorship fee or buy an apartment in the area.

“Fierce competition and the social eagerness to get ahead or at least to stay on par with peers — especially on things symbolizing success, such as house, car and other consumption goods — are still the main forces that drive Chinese society,” said Cai Yong (蔡泳), an assistant professor at the University of North Carolina.

Urbanization — long-established globally as an effective contraception — is magnifying the effect.

As more and more Chinese children enter cities, their parents are forced into competition for limited resources, Cai said.